Some recently-marketed information processors employ the magnetic recording/reproducing device. This recording/reproducing device operates in such a manner that after a flexible magnetic disc is placed on a turntable, this turntable is driven to rotate the disc. While it is rotated, a pickup element is opposed to the disc to perform recording and reproducing of information.
FIGS. 1 through 3 illustrate at respective operation stages an example of the conventional disc clamp device employed in such a recording/reproducing device.
FIG. 1 shows the initial state where a hub frame 1 is positioned at the top dead point. When the magnetic disc 3 is loaded on the turntable 2, the hub frame 1 moves down.
From the hub frame 1 a hub shaft 4 is suspended, to the lower end of this hub shaft 4 a clamp member 5 is attached. This clamp member 5 is composed of a hub 5a and a collet 5b positioned inside the hub 5a, which collet is mounted slidably on the hub shaft 4 via a bearing 6.
As the hub frame 1 moves down, the clamp member 5 also moves down at the same time. Then, a tapered frame 5c of the hub 5a enters first into a center hole 3a of the magnetic disc 3. Thereafter, the center hole 3a is guided by the tapered frame 5c, whereby the provisional centering action is performed. During the above, the hub 5a is brought inside a concave portion 2a formed in the turntable 2 (the state shown in FIG. 2). As the hub frame 1 moves down further, the hub 5a abuts upon the bottom of the concave portion 2a of the turntable 2 and the hub shaft 4 moves up relatively. During the above, the collet 5b is pushed by a clamp spring 7 interposed between the collet 5b and the hub frame 1 and moves down inside the hub 5a. Because plural slits (not shown) are formed in the tapered face 5c of the hub 5a, the tapered face 5c is expanded by the downward movement of the collet 5b. Thus, the center hole 3a of the magnetic disc 3 is pushed in horizontal directions, whereby the position of its axis is corrected to accord with the axis of the concave portion 2a (the subject centering action). During the above, pressing face 5d of the hub 5a pushes the magnetic disc 3 onto the upper surface of the turntable 2 and clamps the same there. The number 8 indicates a return spring to return the collet 5b to its initial pose.
However, the foregoing conventional disc clamp device has the following problems:
(1) As shown in FIG. 1, if the centering action is performed while the hub 5a has the axial discrepany of .DELTA.x relative to the axial center of the turntable 2, a frictional force at abutting portions between the hub frame 1 and the clamp spring 7 becomes large because the pressure of the clamp spring 7 is applied to the hub frame 1, thus, the hub shaft 4 can hardly move in the direction of correcting the axial discrepancy. As a result, the provisional centering action can not take place sufficiently, accordingly, there are such inconveniencies as that the inner periphery of the magnetic disc 3 is bitten into the concave portion 2a of the turntable 2 thereby to suffer damage, or, the tapered face 5c of the hub 5a becomes scratched also.
(2) If the turntable 2 is rotated without eliminating the axial discrepancy, it naturally causes irregular rotation or runout, and the conventional device is hardly applicable, specifically, to a recently-developed high-density information input system where the track pich is narrowed.
(3) Against such inconveniences, they could be overcome by mating accurately the axial center of the hub shaft 4 on which the clamp member 5 is mounted with the axial center of the turntable 2 at the time of assembling, but, this work is not efficient and can not deal with the aged axial discrepancy.
(4) This type of disc clamp device achieves its clamping operation by the use of a one-way closing mechanism. Accordingly, as shown in FIG. 4, the hub frame 1 in the initial state is stationary in the inclined pose. At this time, the clamp member 5 is also held in the inclined pose because it is receiving the pressure of the clamp spring 7. Therefore, as will be clear from the drawing, in order to avoid touching of a jacket 9, having a thickness of t and housing the magnetic disc 3, with one side of the hub 5a, the inclination angle of the hub frame 1 must be selected large. Thus, there is the difficulty that the device could not be made in a thin-sized body.